Cell adhesion chromatography system for biophysical to biochemical analysis of human colon cancer metastasis through the vasculature
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Circulating cell adhesion amidst the high shear environment of the vasculature is central to several physiological and pathophysiological processes, including leukocyte recruitment to sites of inflammation, stem cell homing and cancer metastasis. This process is initiated by selectin-mediated adhesion, the molecular “brakes” that slow cells down relative to bulk fluid flow to facilitate cell-cell signaling and eventual firm cell adhesion. Selectin recognition therefore represents a critical step whereby therapeutic interventions aimed towards the interference of cell homing could be targeted. While the force dependency of these high kon and koff rate interactions has been well described, little understanding exists of the long time- and length-scale interactions of different cell subtypes that would best describe the functional capacity of different cell homing via selectins to systemic peripheral tissues. This limits the adequate description of sustained cell adhesion efficiencies in physiological conditions that predicates the effectiveness of cell homing as well as the design effective therapeutic interventions to selectively attenuate metastasis but not normal cell homing using such criteria. To address this issue, we developed a so-called “cell adhesion chromatography” system, a microfluidic-based device designed for use in conjunction with videomicroscopy for the interrogation of the adhesion behavior of cells over long time- and length-scales. In order to achieve uniform contact of a pulse cell suspension input into a selectin-functionalized parallel plate flow chamber, we designed a feature that enables complete cell settling to the chamber bottom based on Stoke’s flow predictions, increasing contact uniformity of the pulse cell input with the substrate upon entry into the main chromatography channel from ~50 to >95%. Using this configuration, residence time distributions for a pulse input of cells perfused at defined shear stresses were generated based on cell elution times from the cell adhesion chromatography system. Selectin-functionalized substrates delayed cell elution times relative to bovine serum albumin coated-substrates by orders of magnitude in a selectin concentration, shear and cation dependent fashion. Preliminary experiments were also performed to begin to define the differences in efficiencies of healthy (human monocyte) versus malignant (human colon carcinoma) cell adhesion to selectins in shear flow. Our results suggest significant differences in the functional capacity of healthy versus malignant cells to sustain adhesion in shear flow and that cell adhesion chromatography is a new tool that provides unique insight into the process of cell adhesion in fluid flow.